• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.129-134
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• 2011

In this paper, the confined single slot jet impingement is investigated numerically. Although the geometry of the jet impingement is simple, the flow pattern of the jet impingement is complex and the numerical results of the jet impingement is affected much by numerical methods. The first goal of this study is to analyze the effects of Reynolds models and numerical spatial discretization schemes on the results of heat transfer performance and the flaw characteristics and to select the best method. Various versions of the low Reynolds number k-epsilon turbulence models are compared. Using the selected numerical method, the flow field and heat transfer characteristics of confined single slot jet impingement on a moving plate are analyzed.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.272-277
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• 2000

The heat transfer characteristics of confined turbulent slot jet impingement on the flat plate with square rods(turbulence promoter) have been experimentally investigated at different nozzle configuration. The effects of jet Reynolds number (Re=3900, 5800, 7800, 9700), dimensionless slot-to-plate distance(H/B=4, 6, 8) and clearance(c) between square rods and the plate were examined. Measurement of heat transfer rate were conducted using naphthalene sublimation technique. When square rods were inserted over the heat transfer surface, heat transfer rate was slightly increased in the wall jet region and the sharp-edged orifice nozzle was heigher than squared orifice nozzle.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.119-124
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• 2000

The heat transfer characteristics of confined turbulent slot jet impingement on the flat plate with square rods(turbulence promoter) have been experimentally investigated. The effects of jet Reynolds number (Re=3900, 5800, 7800, 9700), dimensionless slot-to-plate distance(H/B=4, 6, 8) clearance(c) between square rods and the plate, and the length(d) of a side of the square rod were examined. Measurement or heat transfer rate were conducted using naphthalene sublimation technique. When square rods were inserted over the heat transfer surface, heat transfer rate was slightly increased in the wall jet region.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.281-285
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• 2005

Viscous solutions of supersonic jet impinging on a flat wall in a confined plenum are simulated using three-dimensional Navier-Stokes solver. A confined plenum was designed for simulating the missile launch and analyzing the behavior of the exhaust plume, which were accompanied by complex flow interactions with shock and boundary layer. Concerns of this paper are to show accurate simulation of internal flow in confined plenum and to demonstrate the jet flow structure when the jet interacts with a small opening on the side. Objectives of this numerical simulation are to understand the effect of changing the plume exit area of the plenum. Pressure and temperature rise at certain position in the plenum are traced and compared with test data.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.93-98
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• 2000

An experimental investigation on heat transfer characteristics of two-dimensional heated blocks using a confined impinging slot jet has been performed. At p/w=1, the effects of jet Reynolds number($Re=3900{\sim}12000$), dimensionless nozzle to block distance(H/B=1, 2, 4, 6) and nozzle type have been examined with five isothermally heated blocks. With the measurement of jet mean velocity and turbulence intensity distributions at nozzle exit, initially turbulent regimes, are classified. To clarify local heat transfer characteristics, naphthalene sublimation technique were used. The local and average heat transfer of heated blocks increase with the sharp-edged nozzle and increasing jet Reynolds number.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.835-840
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• 2009

In this paper, confined multiple slot jet impingement with exhaust ports is investigated numerically. A flow cell, defined as volume sectioned by the impingement and confinement surfaces and the centerlines of adjacent nozzle and exhaust port, is chosen for computational domain. The effects of Reynolds number and geometrical parameters on the heat transfer performance and the flow characteristics are studied. For turbulence, the Abe-Kondoh-Nagano version of the low-Reynolds k-$\varepsilon$ model is employed. The results showed that the local Nusselt number distribution is shifted down and show poor heat transfer performance for small Reynolds number and small ratio of the lateral and axial length of flow cell. The rest of range, except the range of the shift phenomenon, can be classified into three groups by heat transfer characteristics.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.8
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• pp.714-721
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• 2005

The water jet impingement cooling with boiling is one of the techniques to remove heat from high heat flux equipments. The configuration of surface roughness is one obvious condition of affecting the performance on heat transfer in nucleate boiling, The present study investigates the water jet impinging single-phase convection and nucleate boiling heat transfer for the effect of surface roughness to enhance the heat transfer in free surface and submerged jet. The distributions of the averaged wall temperature as well as the boiling curves are discussed. Jet velocities are varied from 0.65 to 1.7 m/s. Surface roughness by sand blast and sand paper varies from 0.3 to 2.51 ${\mu}m$ and cavity shapes on surface are semi-circle and v-shape, respectively The results showed that higher velocity of the jet caused the boiling incipience to be delayed more. The incipient boiling and heat transfer increase with increasing surface roughness due to a large number of cavities of uniform size.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.12
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• pp.1670-1677
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• 2000

An experimental investigation on heat transfer characteristics of two-dimensional heated blocks using a confined impinging slot jet has been performed. The effect of jet Reynolds number(Re=3900, 5800, 9700), streamwise block spacing(p/w=0.5, 1, 1.5) and dimensionless nozzle to block distance(H/B=1, 2, 4, 6) have been examined with five isothermally heated blocks. With the measurement of jet mean velocity and turbulence intensity distributions at nozzle exit, initially turbulent regimes, are classified. To clarify local heat transfer characteristics, naphthalene sublimation technique as used. The maximum Nusselt number at the stagnation point for the jet Reynolds number is occurred at H/B=4. Besides, the local and a average heat transfer of heated blocks increase with decreasing streamwise block spacing and increasing jet Reynolds number.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.125-131
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• 2000

The local heat/mass transfer coefficients for arrays of impinging circular air jets on a plane surface are determined by means of the naphthalene sublimation method. Spent fluid makes a crossflow in the confined space. The crossflow reduces heat/mass transfer at the small gap distance between the jet plate and impingement surface because of reentrainment of the spent fluid. The present study suggests a new exhaust system having effusion holes in the impinging jet plate. The spent air flow out after impingement just through effusion holes located in the upper plate. This system increases heat/mass transfer coefficients and uniformity for small gap distances$(H/d{\leq}2)$

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.496-503
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• 2003

An experimental study has been performed on thermal transport from an aluminum foam heat sink under a confined impinging air jet. Three kinds of aluminum foam heat sinks with 10, 20 and 40 PPI and a conventional pin-fin heat sink are tested in the present study. The jet Reynolds number is varied in the range of Re=667～5672 The effect of the confinement disk diameter and the distance between the confinement disk and the heater surface on the averaged Nusselt number is investigated in detail. The results are also compared with those of the unconfined impinging air jet. The critical distance, at which thermal performance shows a minimum compared to the unconfined jet impinging, will be described in terms of the Reynolds number and the pore density of the aluminum foam.